This invention relates generally to improvements in the storage stability of blood platelets or thrombocytes. More particularly, this invention relates to a platelet composition having improved storage stability by the addition of particular chemical compounds.
Whole blood contains various components such as red blood cells, white blood cells, blood platelets, and plasma (which include both glycoproteins and serum). These various components may be separated by centrifugation means which are well known to those skilled in this art. For example, when whole blood is subjected to centrifugal forces, the plasma and platelets, being the lighter fraction, accumulate at the top of the centrifuge container and may be removed from the other components of the whole blood. If this plasma/platelet fraction is subsequently subjected to further centrifugal force, the platelets tend to the bottom and the plasma to the top of the centrifuge container. The platelet-rich lower fraction may then be removed, re-suspended in a small amount of plasma, and stored as such for subsequent transfusion. A 500-milliliter unit of whole blood produces from 40 to 50 milliliters of this platelet concentrate suspended in plasma. The plasma concentrate is stored in plastic bags on a rotating platform to inhibit the settling out of the platelets.
Blood platelets are produced in the bone marrow. They circulate in the bloodstream and are essential in normal clot formation.
Certain classes of persons, such as leukemics, experience platelet insufficiency, a condition known as thrombocytopenia. Such persons, on occasion, require an infusion of platelets.
Platelet concentrates obtained from healthy blood donors have a shelf-life of about three days, after which time they are of no clinical value because, when transfused, they are rapidly removed from the circulation. Thousands upon thousands of platelet concentrates become outdated before they can be used clinically because of the relatively short storage lifetime of platelet concentrates.
Platelets have a life span in the bloodstream of about seven to ten days. They are removed from circulation by becoming attached to a cell in the liver or spleen. The platelet is pulled into the cell and broken down into various components. The mechanism which some believe to account for this process is the removal of sialic acid residues from the platelets. In this connection, see "Effects on Platelet Function of Removal of Platelet Sialic Acid by Neuraminidase", 32 Lab. Invest. 476 (1975) (Greenberg et al.).
The search has continued concerning the problem of platelet lifetime in storage. This invention was made as a result of that search.